The present invention relates to an apparatus, incorporated in an X-ray photographing apparatus, for feeding a sheet film and, more particularly, to a sheet film feeder for feeding a sheet film from a magazine, which houses unphotographed sheet film, to a sheet film holder which is movable to a photographing position.
In an X-ray photographing apparatus, a sheet film feeder and a sheet film holder, which moves between a waiting position and a photographing position, are provided. During X-ray photographing, a sheet film is fed from the unphotographed film housing magazine to the sheet film holder at the waiting position by the sheet film feeder. The sheet film holder which has received the sheet film at the waiting position holds the sheet film and is moved to the photographing position. X-rays, radiated from an X-ray tube, pass through a patient, and internal portions of the patient are imaged on the sheet film. When this X-ray radiation is terminated, the sheet film holder is returned from the photographing position to the waiting position. The photographed sheet film is taken from the sheet film holder and housed in the photographed film housing magazine. Thus, one X-ray photographing cycle is completed.
In the above X-ray photographing apparatus, the sheet film is arranged substantially perpendicular to a moving direction of the sheet film holder and housed in the unphotographed film housing magazine. Therefore, after the sheet film is taken from the unphotographed film housing magazine, it must be rotated substantially through 90.degree. and moved to the sheet film holder.
For this reason, in a conventional sheet film feeder disclosed in Japanese Patent Disclosure (Kokai) No. 55-33137, a plurality of pairs of rollers for clamping and moving the sheet film are arranged between the unphotographed film housing magazine and the sheet film holder. The sheet film taken from the magazine is sequentially transported from one pair of rollers to another. Thus, the sheet film is rotated through about 90.degree. and fed to the sheet film holder.
At this time, in order to transport the sheet film properly from one pair of rollers to another, all the pairs of rollers must be controlled to rotate at an equal rotating speed. A feed-back control means may be used to detect rotating speeds of each roller pair and to maintain them at a predetermined rotating speed. However, not one but a plurality of pairs of rollers must be simultaneously feedback-controlled. For this reason, a very complex apparatus is required to realize this feedback control. Furthermore, a delay of response occurs, i.e., each pair of rollers may require a time longer than a predetermined time to attain a target speed. In this case, since the rotating speed of each pair of rollers is not equal to each other, the sheet film is sometimes loosened when it is transported from one pair of rollers to another. Because of this loosening, the sheet film is bent and damaged.